Polycaprolactone stability

Amine cured polycaprolactones, stabilized with a carbodiimide, have similar resistance to polyethers. 

Polybutadienes, polycaprolactones, polycarbonates, and amine-terminated polyethers (ATPEs) are shown in Scheme 4.4 as examples of other commercially available polyols. They are all specialty materials, used in situations where specific property profiles are required. For example, ATPEs are utilized in spray-applied elastomers where fast-reacting, high-molecular-weight polyamines give quick gel times and rapid viscosity buildup. Polycarbonates are used for implantation devices because polyuredtanes based on them perform best in this very demanding environment. Polycaprolactones and polybutadienes may be chosen for applications which require exceptional light stability, hydrolysis resistance, and/or low-temperature flexibility. 

Considering the high hydrophobicity of the palmitoyl side chain and the rigidity of the polymer backbone, we assumed that poly(N-palmitoylhydroxyproline ester) would degrade somewhat more slowly than poly (lactic acid) or polycaprolactone. In order to confirm this hypothesis, a series of long-term stability and degradation studies have been performed over the last 2 years at MIT (22). 

All liposphere formulations prepared remained stable during the 3-month period of the study, and no phase separation or appearance of aggregates were observed. The difference between polymeric lipospheres and the standard liposphere formulations is the composition of the internal core of the particles. Standard lipospheres, such as those previously described, consist of a solid hydrophobic fat core composed of neutral fats like tristearin, whereas, in the polymeric lipospheres, biodegradable polymers such as polylactide or polycaprolactone were substituted for the triglycerides. Both types of lipospheres are thought to be stabilized by one layer of phospholipid molecules embedded in their surface. 

Later work by Suzuki and Tokiwa(55,56,57) in which they evaluated the stability of polyesters to lipases confirmed the work of Potts. Potts(58) demonstrated the biodegradation of polycaprolactone which he used in the fabrication of agricultural articles, such as plant pots. J. P. Kendnck(59) demonstrated that amorphous regions of polyesters were more readily biodegraded than crystalline regions. 

Among the polyurethane, polyester, and polyamide thermoplastic elastomers, those with polyether-based elastomer segments have better hydrolytic stability and low temperature flexibility, whereas polyester-based analogues are tougher and have the best oil resistance (43). Polycaprolactones and aliphatic polycarbonates, two special types of polyesters, are used to produce premium-grade polyurethanes (12). 

C. Racles, T. Hamaide, Macromol. Chem. Phys., 2005, 206, 1757-1768. Synthesis and characterization of water soluble saccharide functionalized polysiloxanes and their use as polymer surfactants for the stabilization of polycaprolactone nanoparticles. ... 

It is considered that the polyurethanes based on oleochemical polyols, dimer acids and dimer alcohols, PTHF and PC-polyols lead to polyurethanes with excellent hydrolytic stability. Polycaprolactone (PCL) polyols and poly (butylene adipate) lead to polyurethanes with good hydrolytic stability, but use of poly (diethylene glycol adipate) give polyurethanes with poor hydrolytic resistance. 

Racles C, Hamaide T (2005). Synthesis and Characterization of Water Soluble Saccharide Functionalized Polysiloxanes and Their Use as Polymer Surfactants for the Stabilization of Polycaprolactone Nanoparticles. Macromol. Chem. and Phys. 206 1757-1768. 

Figure 1. SEM and AFM images of nanoparticles stabilized with nonionic or anionic siloxane surfactants (a) polycaprolactone, (b) polysulfone, (c) crosslinked PDMS, and (d) poly(siloxane-azomethine)...

P. Matzinos, V. Tserki, A. Kontoyiannis, and C. Panayiotou, Processing and characterization ofstarch/polycaprolactone products. Polym. Degrad. Stabil. 77,17-24 (2002). 

Polycaprolactones possess good low-temperature impact strength for paintable body panels, good fuel and oil resistance, and hydrolytic stability for seals, gaskets, and belting. Polycaprolactones have fast crystallization rates, high crystallinity, and are generally easily processed into complex parts. 

Polyester polyadipates have improved oil and chemical resistance, but slightly lower hydrolytic stability than polycaprolactones which are used for seals, gaskets, and beltings. 

Tillman BW, Yazdani SK, Lee SJ, Geary RL, Atala A and Yoo JJ, The in vivo stability of electrospun polycaprolactone-collagen scaffolds in vascular reconstruction , Biomaterials, 2009,30(4), 583-588. 

Polyesters have, as a generalization, certain property advantages over polyethers with respe t to strength, oil resistance, etc. Hence many attempts have been made to achieve polyester types of improved hydrolytic stability resulting in the development and establishment of the polycaprolactone series and of the carbonate types, both shown in Table 1.5. 

The addition of carbodiimides, e.g. Staboxal PCD, which is supplied by Bayer, to poly(ester-urethanes) is one of the most effective ways to stabilize them against hydrolysis. Also the polyurethane structure can be tailored for better hydrolysis resistance through elimination or reduction of the ester groups present in the polyol. Hydrolysis resistance increases in the order of ether > polycaprolactone > polyester. Satrastab, developed by SATRA (Shoe and Allied Trades Research Association, Kettering, England), is also claimed to be an effective hydrolysis stabilizer for formulated polyurethanes in poromeric footwear materials. 

COMPARISON OF HYDROLYTIC STABILITY OF POLYURETHANE ELASTOMERS BASED ON POLYETHER AND POLYCAPROLACTONE... 

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